Chang Tsung-Ming, Lu Po-Liang, Li Hsuan-Hui, Chang Chung-Yu, Chen Tun-Chieh, Chang Lin-Li
Department of Microbiology, Faculty of Medicine (Graduate Institute of Medicine), College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
J Chemother. 2007 Oct;19(5):488-94. doi: 10.1179/joc.2007.19.5.488.
DNA sequencing and real-time PCR were used to evaluate the gyrA and parC mutations, AcrAB efflux pump over-expression, and their correlation with high-level resistance to fluoroquinolones in 74 fluoroquinolone-resistant clinical Escherichia coli isolates recently collected in Taiwan. RAPD analysis revealed high clonal diversity. Isolates with four to five mutations (especially Ser83Leu, Asp87Asn [or Asp87Tyr], and Ala93Thr in gyrA and Ser80Ile and Glu84Gly in parC) had increased resistance levels. The acrA gene was over-expressed in 51% of 74 resistant isolates. The trend was towards increased fluoroquinolone MICs in isolates with both multiple mutations in the quinolone-resistance determining region (QRDR) and over-expression of the AcrAB efflux pump. Furthermore, acrA gene over-expression was significantly correlated with cross-resistance to beta-lactams including piperacillin, amoxicillin, clavulanic acid, and cefazolin. In conclusion, mutations in the QRDR are the primary mechanism for increasing fluoroquinolone resistance, and in combination with efflux pump over-expression, contribute to high-level resistance.
采用DNA测序和实时荧光定量PCR技术，对台湾近期收集的74株耐氟喹诺酮类临床大肠埃希菌分离株的gyrA和parC基因突变、AcrAB外排泵过表达及其与氟喹诺酮类高水平耐药的相关性进行评估。随机扩增多态性DNA分析显示高度的克隆多样性。具有4至5个突变（特别是gyrA中的Ser83Leu、Asp87Asn[或Asp87Tyr]和Ala93Thr以及parC中的Ser80Ile和Glu84Gly）的分离株耐药水平增加。在74株耐药分离株中，51%的分离株acrA基因过表达。喹诺酮耐药决定区（QRDR）存在多个突变且AcrAB外排泵过表达的分离株中，氟喹诺酮类最低抑菌浓度有升高趋势。此外，acrA基因过表达与对包括哌拉西林、阿莫西林、克拉维酸和头孢唑林在内的β-内酰胺类药物的交叉耐药显著相关。总之，QRDR中的突变是氟喹诺酮类耐药增加的主要机制，与外排泵过表达共同导致高水平耐药。
